Further evidence that an episode of premature labor is a pathologic state: involvement of the insulin-like growth factor system.

INTRODUCTION: Approximately 47% of women with an episode of preterm labor deliver at term; however, their infants are at greater risk to be small for gestational age and for neurodevelopmental disorders. In these cases, a pathologic insult may disrupt the homeostatic responses sustaining pregnancy. We tested the hypothesis of an involvement of components of the insulin-like growth factor (IGF) system.

METHODS: This is a cross-sectional study in which maternal plasma concentrations of PAPP-A, PAPP-A2, IGFBP-1, and IGFBP-4 were determined in the following groups of women: 1) no episodes of preterm labor, term delivery (controls, n=100); 2) episode of preterm labor, term delivery (n=50); 3) episode of preterm labor, preterm delivery (n=100); 3); 4) pregnant women at term not in labor (n= 61); and 5) pregnant women at term in labor (n= 61). Pairwise differences in maternal plasma concentrations of PAPP-A, PAPP-A2, IGFBP-1, and IGFBP-4 among study groups were assessed by fitting linear models on log transformed data and included adjustment for relevant covariates. Significance of the group coefficient in the linear models was assessed via t-scores, with p<0.05 being deemed a significant result.

RESULTS: Compared to controls, 1) women with an episode of premature labor, regardless of a preterm or a term delivery, had higher mean plasma concentrations of PAPP-A2 and IGFBP-1 (each p<0.05); 2) women with an episode of premature labor who delivered at term also had a higher mean concentration of PAPP-A (p<0.05); and 3) acute histologic chorioamnionitis and spontaneous labor at term were not associated with significant changes in these analytes.

CONCLUSION: An episode of preterm labor involves the IGF system, supporting the view that the premature activation of parturition is a pathologic state, even in those women who delivered at term.